TWI644118B - Ultrasonic element - Google Patents

Abstract

An ultrasonic element includes: a surface contact layer, a signal receiving layer, and a signal transmitting layer which are arranged in a stack; the surface contact layer has a contact surface for contacting a body to be sensed; and the signal transmitting layer is used for generating and Sending a sensing signal; the signal receiving layer is used to receive the sensing signal; the natural frequency of the surface contact layer is defined as F ₁ , the natural frequency of the signal receiving layer is defined as F ₂ , and the signal transmitting layer The natural frequency of is defined as F ₃ , and the frequency of the sensing signal is defined as F ₀ ′; wherein at least one of F ₁ , F ₂ , and F ₃ is equal to F ₀ ′. The invention enables the signal strength output by the sensing device to be enhanced, and the sensing accuracy is improved.

Description

Ultrasonic component

The invention relates to an ultrasonic element.

In recent years, electronic devices such as mobile phones, computers, game consoles, etc. generally use acoustic wave sensing elements instead of capacitive sensing elements. The acoustic wave sensing elements have advantages such as long life and high resolution. The sonic sensing element usually includes a signal receiving unit and a signal transmitting unit. During operation, the signal transmitting unit sends a sensing signal. The part of the sensing signal that reaches the interface is absorbed by the touch finger, and part of the sensing signal is reflected to the signal receiving unit. The reflected sensing signals are converted into electrical signals to form touch information. It has been found that the transmission of the sensing signal in the sonic sensing element usually results in a loss of energy, thereby affecting the strength of the sensing signal and the accuracy of the sensing.

In view of this, it is necessary to provide an ultrasonic element capable of improving the strength of a sensing signal.

An ultrasonic element includes: a surface contact layer, a signal receiving layer, and a signal transmitting layer which are arranged in a stack; the surface contact layer has a contact surface for contacting a body to be sensed; and the signal transmitting layer is used for generating and Sending a sensing signal; the signal receiving layer is used to receive the sensing signal; the natural frequency of the surface contact layer is defined as F ₁ , the natural frequency of the signal receiving layer is defined as F ₂ , and the signal transmitting layer The natural frequency is defined as F ₃ , and the frequency of the sensing signal is defined as F 0 ′; wherein at least one of F ₁ , F ₂ , and F ₃ is equal to F ₀ ′.

Preferably, the F ₀ ′, F ₁ , F ₂ , and F ₃ satisfy at least one of the following conditions: F ₁ , F ₂ and F ₀ ′ are equal; F ₂ , F ₃ and F ₀ ′ are equal; F ₁ , F _{3 is} equal to F ₀ '; F ₁ , F ₂ , and F ₃ are all equal to F ₀ '.

Preferably, the wave velocity of the surface contact layer is defined as C ₁ , the wave velocity of the signal receiving layer is defined as C ₂ , and the wave velocity of the signal transmitting layer is defined as C ₃ ; the thickness of the surface contact layer is defined as H ₁ The thickness of the signal receiving layer is defined as H ₂ , and the thickness of the signal transmitting layer is defined as H ₃ ; and the ratio of the thickness to the wave velocity in the surface contact layer, the signal receiving layer, and the signal transmitting layer is at least both equal.

Preferably, the H ₁ , H ₂ , H ₃ , C ₁ , C ₂ , C ₃ satisfy at least one of the following conditions: H ₁ : H ₂ = C ₁ : C ₂ ; H ₂ : H ₃ = C ₂ : C ₃ ; H ₁ : H ₃ = C ₁ : C ₃ ; H ₁ : H ₂ : H ₃ = C ₁ : C ₂ : C ₃ .

Preferably, the signal receiving layer includes a first piezoelectric layer, and the signal transmitting layer includes a second piezoelectric layer; a thickness of the surface contact layer is defined as H ₁ , and a thickness of the first piezoelectric layer is defined as H ₂ , the thickness of the second piezoelectric layer is defined as H ₃ ; the wave velocity of the surface contact layer is defined as C ₁ , the wave velocity of the first piezoelectric layer is defined as C ₂ , and the second piezoelectric layer The wave velocity of is defined as C ₃ ; the ratio of the thickness to the wave velocity in the surface contact layer, the first piezoelectric layer, and the second piezoelectric layer is at least both equal.

Preferably, the H ₁ , H ₂ , H ₃ , C ₁ , C ₂ , C ₃ satisfy at least one of the following conditions: H ₁ : H ₂ = C ₁ : C ₂ ; H ₂ : H ₃ = C ₂ : C ₃ ; H ₁ : H ₃ = C ₁ : C ₃ ; H ₁ : H ₂ : H ₃ = C ₁ : C ₂ : C ₃ .

Preferably, it includes a first adhesive layer and a second adhesive layer, the surface contact layer and the signal receiving layer / signal transmitting layer are connected and signal coupled through the first adhesive layer, and the signal transmitting layer It is connected to the signal receiving layer through the second adhesive layer and performs signal coupling.

Preferably, the thickness of the first adhesive layer is defined as H _m1 , and the thickness of the second adhesive layer is defined as H _m2 . The surface of the contact layer has a thickness H _1, the signal-receiving layer of a thickness of H _2, the thickness H of the signal transmission layer ₃ is defined as the minimum value among H _min. The H _m1 <H _min / 10, and the H _m2 <H _min / 10.

Preferably, a driving signal is provided. The frequency of the driving signal is defined as F _{0. The} driving signal is used to drive the signal transmitting layer to generate a sensing signal. The frequency F _{0 of} the driving signal and the frequency F of the sensing signal are provided. ₀ 'Equal.

Preferably, the sensing signal is an ultrasonic signal.

Compared with the conventional technology, the present invention utilizes the principle of co-frequency resonance to provide an ultrasonic element. The driving signal / sensing signal of the ultrasonic element is consistent with the natural frequency of the internal material of the ultrasonic element to reduce the acoustic signal in the The attenuation during the transmission of the acoustic wave signal can improve the strength of the signal and the accuracy of the sensing to a certain extent.

100‧‧‧ electronic device

10, 20'‧‧‧ Ultrasonic components

1.1'‧‧‧ surface contact layer

11, 11'‧‧‧ contact surface

2, 2'‧‧‧ signal receiving layer

21, 21'‧‧‧ First electrode

22, 22'‧‧‧ the first piezoelectric layer

3, 3'‧‧‧ signal sending layer

31, 31'‧‧‧Second electrode

32, 32'‧‧‧Second piezoelectric layer

33, 33'‧‧‧ Third electrode

4, 4'‧‧‧ Adhesive layer

41, 41'‧‧‧ first adhesive layer

42, 42'‧‧‧Second adhesive layer

FIG. 1 is a schematic diagram of a three-dimensional structure of an electronic device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional structure taken along the line III-III in FIG. 1.

FIG. 3 is a schematic cross-sectional structure view of an ultrasonic element according to a second embodiment of the present invention.

Please refer to FIG. 1 and FIG. 2 at the same time. FIG. 1 is a schematic diagram of the three-dimensional structure of the electronic device 100 according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional structure taken along the line III-III in FIG. 1. The electronic device 100 may be an electronic device such as a computer, a television, or a mobile phone, but is not limited thereto.

In this embodiment, the electronic device 100 includes an ultrasonic element 10 for sensing a touch operation. The ultrasonic element 10 includes a surface contact layer 1, a signal receiving layer 2, a signal transmitting layer 3, and an adhesive layer 4. The surface contact layer 1 has a contact surface 11 which is in contact with the object to be sensed. The surface contact layer 1 is in contact with an object to be measured (such as a finger) through the contact surface 11. The ultrasonic element 10 is not limited to sensing a touch operation. For example, in other embodiments, the ultrasonic element 10 may be applied to sensing blood pressure in the biological field, but is not limited thereto. In this embodiment, the signal receiving layer 2 is disposed on a side of the surface contact layer 1 different from the contact surface 11, and the signal transmitting layer 3 is disposed on a side of the signal receiving layer 2 away from the surface contact layer 1. The signal sending layer 3 is used to generate and send the sensing signal, and the signal receiving layer 2 is used to receive the reflected sensing signal. In other embodiments, the positional relationship between the signal transmitting layer 3 and the signal receiving layer 2 is not limited. For example, the signal transmitting layer 3 may be disposed on a side of the surface contact layer 1 different from the contact surface 11 and the signal receiving layer 2 The signal transmission layer 3 can be disposed on a side of the signal transmission layer 3 away from the surface contact layer 1.

The adhesive layer 4 has a signal coupling effect. In this embodiment, the adhesive layer 4 includes a first adhesive layer 41 and a second adhesive layer 42. The surface contact layer 1 and the signal receiving layer 2 are connected by the first adhesive layer 41, and the first adhesive layer 41 performs signal coupling between the surface contact layer 1 and the signal receiving layer 2. . The second adhesive layer is used between the signal transmitting layer 3 and the signal receiving layer 2. 42 is connected, and the second adhesive layer 42 performs signal coupling between the signal transmitting layer 3 and the signal receiving layer 2.

In this embodiment, the ultrasonic element 10 is a touch-sensitive switch capable of sensing a touch operation. The signal receiving layer 2 includes a first electrode 21 and a first piezoelectric layer 22. In other embodiments, the signal receiving layer 2 may include an upper electrode, a lower electrode, and a piezoelectric layer (not shown) sandwiched between the upper and lower electrodes. The signal transmitting layer 3 includes a second electrode 31, a second piezoelectric layer 32, and a third electrode 33. The second piezoelectric layer 32 is interposed between the second electrode 31 and the third electrode 33. The first piezoelectric layer 22 and the second piezoelectric layer 32 are materials having piezoelectric characteristics. The second electrode 31 and the third electrode 33 apply a voltage to the second piezoelectric layer 32, and the second piezoelectric layer 32 vibrates under the action of the voltage to emit an ultrasonic sensing signal. When the measured object is placed on the surface contact layer 1, the ultrasonic wave is affected by the measured object, and the emitted ultrasonic wave changes accordingly. The ultrasonic wave is reflected by the sensing object such as a finger to the signal receiving layer. 2 is converted into a signal and output.

According to the characteristics of the wave, the following relational expression (1) is satisfied: C = F × λ ... Equation (1), where C is the wave speed, F is the frequency, and λ is the wavelength. The magnitude of the wave velocity is determined by the nature of the material of the object. When the material and thickness are known, according to the calculation method of natural frequency, considering the total reflection of the sound wave on the surface of the object, the wavelength and the thickness of the object can be Satisfying λ = 2H, the frequency F of the object, that is, the natural frequency can be calculated by the relationship (1): C = F × λ. In this embodiment, the materials of the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3 are the first material, the second material, and the third material, and the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3 are in order. The corresponding wave velocities are C ₁ , C ₂ , and C _{3, respectively} . Knowing the thickness H ₁ of the surface contact layer 1 and the wave velocity C ₁ of the surface contact layer ₁ and letting the wavelength of the surface contact layer be λ ₁ , the following relation (2) ~ (3) holds: 2 × H ₁ = λ ₁ … Formula (2)

C ₁ / λ ₁ = F ₁ … Formula (3)

Thereby, the natural frequency F _{1 of the} surface contact layer 1 can be obtained.

An electric signal with a frequency F ₀ is provided as a driving signal. The frequency F _{0 of} the driving signal is equal to the frequency F _{1 of the} surface contact layer 1. The driving signal is used to drive the signal transmitting layer 3 to generate an ultrasonic sensing signal. According to the characteristics of the piezoelectric material, the signal transmitting layer 3 does not change the frequency of the signal after the driving signal is converted into an ultrasonic sensing signal, so that the frequency of the sensing signal is F ₀ ', then the following (4) The relationship holds: F ₀ '= F ₀ = F ₁ … Equation (4)

Therefore, the sensing signal from the signal transmitting layer 3 can achieve the same frequency resonance with the surface contact layer 1. In this embodiment, the signal receiving layer 2 includes a first electrode 21 and a first piezoelectric layer 22. Since the thickness of the first electrode 21 is much smaller than that of the first piezoelectric layer 22, the thickness of the signal receiving layer 2 ignores the first The thickness of an electrode 21 and the thickness of the signal receiving layer 2 are only the thickness of the first piezoelectric layer 22. The thickness of the signal receiving layer 2 is set to H ₂ , and the wave velocity of the signal receiving layer 2 is known to be C ₂ , so that the natural frequency of the signal receiving layer 2 F ₂ = F ₀ ′, so that the sensing signal and the signal receiving layer 2 Realize the same frequency resonance. Let the wavelength of the signal receiving layer 2 be λ ₂ . Then the following relationship (5) ~ (6) holds: C ₂ / F ₂ = λ ₂ … Formula (5)

λ _2/2 = H ₂ ... of formula (6)

Therefore, the thickness H _{2 of} the signal receiving layer 2 under the condition of F ₂ = F ₀ ′ can be obtained.

The signal transmitting layer 3 includes a second electrode 31, a first piezoelectric layer 32, and a third electrode 33. Since the thickness of the second electrode 31 and the third electrode 33 is much smaller than that of the second piezoelectric layer 32, the thickness of the signal transmitting layer 3 Ignoring the thicknesses of the second electrode 31 and the third electrode 33, the thickness of the signal transmitting layer 3 is only the thickness of the second piezoelectric layer 32. The thickness of the signal transmission layer 3 is set to H _3. The wave velocity of the signal transmission layer 3 is known to be C _{3. The} signal transmission layer 3 is used to receive a driving signal to generate a sensing signal. Let the natural frequency F ₃ = F _{0 of the} signal transmission layer 3 to achieve the same frequency resonance between the signal transmission layer and the driving signal. Let the wavelength of the signal transmission layer 3 be λ ₃ . Then the following relation (7) ~ (8) holds: C ₃ / F ₃ = λ ₃ … Equation (7)

λ _3/2 = H ₃ ... of formula (8)

Thus, the thickness H _{3 of} the signal transmission layer 3 under the condition of F ₃ = F ₀ can be obtained.

In the present embodiment, the thickness of the first adhesive layer 41 is set to H _M1, the thickness of the second adhesive layer is set to H _M2; thickness H of the surface of the contact layer 1 takes _1, the signal receiving layer has a thickness H ₂ The minimum value of the thickness H _{3 of the} signal transmission layer is H _min , and H _m1 and H _m2 are both less than H _min / 10, that is, H _m1 <H _min / 10 and H _m2 <H _min / 10. Since the thicknesses of H _m1 and H _m2 are smaller than those of H ₁ , H ₂ , and H ₃ , the thicknesses of H _m1 and H _m2 are ignored during the transmission of the sensing signal in this embodiment.

Frequency frequency F ₀ F ₀ / sensing signal of the driving signal 'frequency _1, the signal receiving surface of the contact layer a layer F of a frequency F _2, the signal transmission frequency layer F ₃ is equal, the following equation (9) the relation True: F ₀ '= F ₀ = F ₁ = F ₂ = F ₃ … Equation (9)

Whereby the frequency can be obtained 'in contact with the surface layer of the frequency F 1, signal reception layer ₀ / F _{0 1} 10 ultrasonic element driving signal / sensing signal frequency F frequency F _2, F ₃ signal transmission layers are equal. The driving signal / sensing signal achieves the same frequency resonance with the ultrasonic element 10, which can reduce the attenuation of the driving signal / sensing signal during the transmission of the ultrasonic element 10 signal, and can increase the signal strength and sensing to a certain extent Accuracy.

From the formulas (1) to (9), it can be known that the following relationship (10) holds: H ₁ : H ₂ : H ₃ = C ₁ : C ₂ : C ₃ ... Formula (10)

In this embodiment, the wave speeds C ₁ , C ₂ , and C _{3 of the} surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer ₃ and the thickness H _{1 of the} surface contact layer 1 are known. Related parameters. In other embodiments, the known parameter values may be changed, for example, the wave velocity C ₁ , C ₂ , C ₃ and the signal receiving layer 2 of the known surface contact layer 1, signal receiving layer 2, and signal transmitting layer 3 may be changed. The thickness H ₂ / H _{3 of the} / signal transmitting layer 3 is used to further calculate other relevant parameters for achieving resonance.

Optionally, the thicknesses H ₁ , H ₂ , and H ₃ of the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3, and the thickness of _{one of the} surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3 may be specified. Wave velocity, further calculate other relevant parameters to achieve resonance, and then select the appropriate material matching the parameter value as the other two layers, can also achieve the same frequency resonance.

In the above embodiment, the sensing signal and the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3 all achieve the same frequency resonance. In other embodiments, the sensing signal may only transmit co-frequency resonance with one or both of the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3. That is, the frequency F ₀ ′ of the sensing signal is only equal to one or both of the natural frequencies of the surface contact layer 1, the signal receiving layer 2, and the signal transmitting layer 3.

Please refer to FIG. 3, which is a schematic cross-sectional structure diagram of the ultrasonic element 20 according to the second embodiment of the present invention. In this embodiment, functions of the same elements as those in the first embodiment are the same, and details are not described herein again. The ultrasonic element 20 includes a surface contact layer 1 ', a signal receiving layer 2', a signal transmitting layer 3 ', and an adhesive layer 4'. The surface contact layer 1 'has a contact surface 11' which is in contact with the body to be sensed. The surface contact layer 1 'is in contact with the measured object (such as a finger, etc.) through the contact surface 11'. The signal receiving layer 2 'is disposed on a side of the surface contact layer 1' different from the contact surface 11 ', and the signal transmitting layer 3' is disposed on the signal receiving layer 2 'away from the surface contact layer 1'. One side. The signal receiving layer 2 'includes a first electrode 21' and a first piezoelectric layer 22 '. The signal transmitting layer 3 ′ includes a second electrode 31 ′, a second piezoelectric layer 32 ′, and a third electrode 33 ′. The second piezoelectric layer 32 ′ is sandwiched between the second electrode 31 ′ and the third electrode 33. 'between.

According to the above analysis, there are: C '= F' × λ ', λ = 2H, and the frequency F' of the object, that is, the natural frequency, can be calculated by the relationship C '= F' × λ '.

In this embodiment, the sensing signal of the ultrasonic element 20 only has the same frequency resonance with the surface contact layer 1 and the signal receiving layer 2. In this embodiment, the material and thickness of the surface contact layer 1 can be specified to obtain C ₁ ′, H ₁ ′. According to the above analysis, the following relationship (11) to (12) holds: 2 × H ₁ ′ = λ ₁ '... Eq. (11)

C ₁ / λ ₁ '= F ₁ ' ... Equation (12)

Thus, the natural frequency F ₁ ′ of the surface contact layer 1 can be obtained.

Providing an electrical signal frequency of ₀₀ F as the frequency driving signal, the driving signal F 'frequency F _1' in contact with the surface layer ₀₀ is equal to 1, the drive signal for driving the signal transmission layer 3 'to produce ultrasound formula Sensing signal, the signal sending layer 3 'converts the driving signal into an ultrasonic sensing signal, the frequency of the signal does not change, and the frequency of the sensing signal is F ₀₀ ', then the following (13) relationship is established : F ₀₀ '= F ₀₀ = F ₁ ' ... Equation (13)

Therefore, the sensing signal from the signal transmitting layer 3 'can achieve the same frequency resonance with the surface contact layer 1'.

In this embodiment, the signal receiving layer 2 'includes a first electrode 21' and a first piezoelectric layer 22 '. Since the thickness of the first electrode 21' is much smaller than that of the first piezoelectric layer 22 ', the signal receiving layer The thickness of 2 'ignores the thickness of the first electrode 21', and the thickness of the signal receiving layer 2 'is only the thickness of the first piezoelectric layer 22'. Disposed signal receiving layer 2 'is a thickness H _2', known in the signal-receiving layer 2 'velocity is C _2', so that the signal-receiving layer 2 'the natural frequency F _2' = F ₀₀ ', so that the sense The signal and the signal receiving layer 2 'realize the same frequency resonance. Signal-receiving layer 2 provided 'wavelength is λ _2'. Then the following relations (14) ~ (15) hold: C ₂ '/ F ₂ ' = λ ₂ '... Equation (14)

λ ₂ '/ 2 = H ₂ ' ... Equation (15)

Thus, the thickness H _{2 of} the signal receiving layer 2 'under the condition of F ₂ ' = F ₀₀ 'can be obtained.

In this embodiment, the surface contact layer 1 ′ and the signal receiving layer 2 ′ are connected by the first adhesive layer 41 ′. The first adhesive layer 41 ′ is connected between the surface contact layer 1 ′ and the surface contact layer 1 ′. Signal coupling is performed between the signal receiving layers 2 '. The signal transmitting layer 3 'and the signal receiving layer 2' are connected by the second adhesive layer 42 ', and the second adhesive layer 42' is between the signal transmitting layer 3 'and the signal receiving layer 2 'Signal coupling between'. The first adhesive layer 41 'of thickness H is set _M1', thickness of the second adhesive layer is set to _M2 H '; the contact layer thickness of the surface taken 1 H _1', the thickness H of the signal-receiving layer ₂ ' The minimum value of the thickness H _{3 of the} signal transmission layer is H _min ', and H _m1 and H _m2 are both smaller than H _min ' / 10, that is, H _m1 '<H _min ' / 10, H _m2 '<H _min ' / 10 . Since the thicknesses of H _m1 ′ and H _m2 ′ are smaller than those of H ₁ ′ and H ₂ ′, the thicknesses of H _m1 and H _m2 are ignored during the transmission of the sensing signal in this embodiment.

In the present embodiment, the frequency of the drive signal F ₀₀ and the sensing signal frequency F ₀₀ 'in contact with the surface layer 1' F. Frequency ₁ ', the frequency of the signal-receiving layer F _2' are equal, the following equation (16) Relationship The formula holds: F ₀₀ '= F ₀₀ = F ₁ ' = F ₂ '... Formula (16)

Whereby to obtain ₂ 'are equal in the sensing signal of an ultrasonic frequency F ₀ element 20' in contact with the surface layer 1 frequency F ₁ 'F-frequency signal-receiving layer. The driving signal / sensing signal and the touch sensing switch 20 realize partial resonance at the same frequency, which can reduce the attenuation of the driving signal / sensing signal during the transmission process of the ultrasonic component signal, and can increase the signal strength and sensitivity to a certain extent. Measurement accuracy.

From the expressions (11) to (16), it can be known that the following relationship (17) holds: H ₁ ′: H ₂ ′ = C ₁ ′: C ₂ ′… Formula (17)

In this embodiment, the wave velocities C ₁ ′, C ₂ ′ of the surface contact layer 1 ′, the signal receiving layer 2 ′, and the thickness H ₁ ′ of the surface contact layer 1 ′ are known. Relevant parameters for measuring the resonance of the signal with the surface contact layer 1 'and the signal receiving layer 2'. In other embodiments, the known parameter values may be changed, for example, the wave velocity C ₁ ′, C ₂ ′, and C ₃ of the known surface contact layer 1 ′, signal receiving layer 2 ′, and signal transmitting layer 3 ′ may be changed. The two of 'and the thickness H ₁ ', H ₂ ', H ₃ ' of the surface contact layer 1 ', the signal receiving layer 2', and the signal transmitting layer 3 'correspond to one of the known wave speeds, and further calculated Other related parameters for realizing resonance between the driving signal / sensing signal and two of the surface contact layer 1 ', the signal receiving layer 2', and the signal transmitting layer 3 '.

Alternatively, the thicknesses H ₁ ′, H ₂ ′, and H ₃ ′ of the surface contact layer 1 ′, the signal receiving layer 2 ′, and the signal transmitting layer 3 ′ may be specified, as well as the surface contact layer 1 ′ and the signal receiving layer 2. ', the signal transmission layer 3' velocity of _{C 1 ', C 2',} C 3 ' with one of the corresponding one of known thickness, other implementations further calculate the driving signal / signal sensing contact with the surface layer 1' The parameters related to the second-layer resonance in the signal receiving layer 2 'and the signal transmitting layer 3', and then selecting a suitable material that matches the parameter value can also achieve the same frequency resonance.

In the second embodiment of the present invention, the driving signal / sensing signal can selectively achieve the same frequency resonance with only the surface contact layer 1 'and the signal receiving layer 2'. In other embodiments, the driving signal / sensing signal also Can selectively achieve the same frequency resonance with the signal receiving layer 2 'and the signal transmitting layer 3', or the drive signal / sensing signal can also selectively achieve the same frequency with the surface contact layer 1 'and the signal transmitting layer 3' Resonance. At this time, at least one of the following relational expressions (18) to (21) holds: F ₂ ′, F ₃ ′ = F ₀₀ ′… Equation (18)

F ₁ ', F ₃ ' = F ₀₀ '... Equation (19)

H ₂ ': H ₃ ' = C ₂ ': C ₃ ' ... Formula (20)

H ₁ ': H ₃ ' = C ₁ ': C ₃ ' ... Formula (21)

In this embodiment, the first electrode 21, the second electrode 31, and the third electrode 33 may be, but are not limited to, copper, silver, molybdenum, titanium, aluminum, tungsten, and indium tin oxide. The first piezoelectric layer 21 and the second piezoelectric layer 32 may be piezoelectric materials such as polyvinylidene fluoride (PVDF), lead zirconate titanate piezoelectric ceramic (PZT), and the like. The material of the surface contact layer 1 may be metal, plastic, glass, or the like, but is not limited thereto.

The above embodiments are only used to illustrate the technical solution of the present invention, but not limited. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or equivalently replaced, and Without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

An ultrasonic element includes: a surface contact layer, a signal receiving layer, and a signal transmitting layer which are arranged in a stack; the surface contact layer has a contact surface for contacting a body to be sensed; and the signal transmitting layer is used for generating and Sending a sensing signal; the signal receiving layer is configured to receive the sensing signal; the improvement is that the natural frequency of the surface contact layer is defined as F ₁ , and the natural frequency of the signal receiving layer is defined as F ₂ , so The natural frequency of the signal transmission layer is defined as F ₃ , and the frequency of the sensing signal is defined as F ₀ ′; where F ₁ = F ₀ ′. The ultrasonic element according to claim 1, wherein the F ₀ ′, F ₂ , and F ₃ satisfy at least one of the following conditions: F _{2 is} equal to F ₀ ′; F _{3 is} equal to F ₀ ′; F ₂ , F _{3 is} all equal to F ₀ '. The ultrasonic element according to claim 1, wherein the wave velocity of the surface contact layer is defined as C ₁ , the wave velocity of the signal receiving layer is defined as C ₂ , and the wave velocity of the signal transmitting layer is defined as C ₃ ; said surface of the contact layer thickness is defined as H _1, the signal-receiving layer thickness is defined as H _2, the signal transmission layer thickness is defined as H _3; contacting the surface layer, the signal-receiving layer, the signal transmission layer thickness The ratio to the wave velocity is at least equal to both. The ultrasonic element according to claim 3, wherein the H ₁ , H ₂ , H ₃ , C ₁ , C ₂ , and C ₃ satisfy at least one of the following conditions: H ₁ : H ₂ = C ₁ : C ₂ H ₂ : H ₃ = C ₂ : C ₃ ; H ₁ : H ₃ = C ₁ : C ₃ ; H ₁ : H ₂ : H ₃ = C ₁ : C ₂ : C ₃ . The ultrasonic element according to claim 1, wherein: the signal receiving layer includes a first piezoelectric layer, and the signal transmitting layer includes a second piezoelectric layer; the thickness of the surface contact layer is defined as H ₁ , so The thickness of the first piezoelectric layer is defined as H ₂ , the thickness of the second piezoelectric layer is defined as H ₃ ; the wave velocity of the surface contact layer is defined as C ₁ , and the wave velocity of the first piezoelectric layer is defined as C ₂ , the wave velocity of the second piezoelectric layer is defined as C ₃ ; the ratio of the thickness to the wave velocity in the surface contact layer, the first piezoelectric layer, and the second piezoelectric layer is equal to at least two. The ultrasonic element according to claim 5, wherein the H ₁ , H ₂ , H ₃ , C ₁ , C ₂ , and C ₃ satisfy at least one of the following conditions: H ₁ : H ₂ = C ₁ : C ₂ H ₂ : H ₃ = C ₂ : C ₃ ; H ₁ : H ₃ = C ₁ : C ₃ ; H ₁ : H ₂ : H ₃ = C ₁ : C ₂ : C ₃ . The ultrasonic element according to any one of claims 1-6, comprising: a first adhesive layer and a second adhesive layer; the surface contact layer and the signal receiving layer / signal transmitting layer are connected by The first adhesive layer is connected and signal coupled, and the signal transmitting layer and the signal receiving layer are connected and signal coupled through the second adhesive layer. The ultrasonic element according to claim 7, wherein the thickness of the first adhesive layer is defined as H _m1 , the thickness of the second adhesive layer is defined as H _m2 , the thickness of the surface contact layer H ₁ , and the signal thickness of the receiving layer is H _2, the thickness H of the signal transmission layer ₃ is defined as the minimum value among H _min, the _{H m1 <H min / 10,} H m2 <H min / 10. The ultrasonic element according to any one of claims 1-6, wherein: a driving signal is provided, and a frequency of the driving signal is defined as F ₀ , and the driving signal is used to drive a signal transmitting layer to generate a sensing signal The frequency F _{0 of} the driving signal is equal to the frequency F ₀ ′ of the sensing signal. The ultrasonic element according to claim 1, wherein the sensing signal is an ultrasonic signal.